1) Field of the Invention
The present invention relates to a technology for feeding a recording medium in an image forming apparatus.
2) Description of the Related Art
A conventional paper feeder picks up a sheet of paper from a pile of paper stacked in a paper feeding tray with a pick-up roller, transfers the paper between a feed roller and a sheet separator to separate the paper, and then carries the paper with a pair of transporting rollers that is disposed in a downstream side. The paper feeder is formed as a separate paper feeding unit that includes the feed roller and the transporting roller from the paper feeding tray.
FIG. 5 is a cross-sectional view of a relevant part of the conventional paper feeder. The paper feeder, in this example, includes four paper trays 101 stacked in a vertical direction. Each of the paper trays contains a paper of a different size. Each of the paper trays 101 includes a paper feeding unit 103. The paper feeding unit 103 includes a pick-up roller 105 that is in contact with the top of the pile of the paper contained in a corresponding paper tray 101, a feed roller 107 that is disposed on a downstream side of the pick-up roller 105 in a paper transporting path 109, and a pair of transporting rollers 111 that carry the paper along the paper transporting path 109.
With this mechanism, if an interval between the paper feeding units 103 varies depending on models of the image forming apparatuses, the paper feeding unit should be manufactured for each model. As a result, single type of the paper feeding unit cannot be commonly used for various models of the image forming apparatus.